Previously, in such machinery, it has not been possible to remove sag which is created when the sheets are heated to deforming temperatures. This is particularly a problem when large sheets of, for example, 30.times.42 inches in size, and larger, are involved.
One of the prime objects of the invention is therefore to provide a clamp frame carrier assembly which is so constructed as to provide a new method of removing sag formed in the sheet when the thermoplastic sheet is raised to thermoforming temperatures. Previously, also, in such machinery, plastic sheet have not, to our knowledge, been molded to only a portion of an underlying panel or product which functions as the mold, and to which the plastic is to adhere to form the article, and the method which has been developed and is disclosed in the present application is able to accomplish this in an efficient and reliable manner, and to do so in a manner which molds two products at a time. In the present case, for example, a single molding operation may utilize a single sheet of plastic and mold it to partially cover the desired areas of both a left hand and right hand door panel for an automotive vehicle.
Still another object of the invention is to provide a thermoforming machine of the character involved which is capable of being used in automotive production lines, operating at the high speeds demanded.
Still another object of the invention is to provide a carrier frame which, with slight modification, may be used reversely to increase the sag or drape in the plastic sheet being processed.
Still a further object of the invention is to provide a sag removing sheet carrier assembly which is capable of stretching the plastic to better condition it from an orientation and stability standpoint.
Still another object of the invention is to provide a method and machine which is capable of processing a wide variety of synthetic plastic sheets such as polystyrene, polyethylene, polyvinyl chloride, polypropylene and others.